As two new generation mainstream wideband wireless communication systems, the Long Term Evolution (LTE) system formulated by 3GPP organization and Worldwide Interoperability for Microwave Access (WiMax) system formulated by WiMax Forum (WMF) and Institute of Electrical And Electronic Engineer (IEEE) have developed rapidly. An important aspect of the research is how to realize the intercommunication between new generation wideband wireless communication system and existing system (including 3GPP2 system), for example, the intercommunication between LTE system and General Packet Radio Service (GPRS) system of 3GPP, the intercommunication between LTE system and Wideband Code Division Multiple Access (WCDMA) system of 3GPP, the intercommunication between CDMA2000 and the HRPD system, etc., but simultaneously it requires minimal influence to the existing system so that the existing system is evolved or updated smoothly. The 3GPP2 system mentioned herein refers to CDMA2000 1X system and the HRPD system formulated by 3GPP2 Standard Organization. While the non-3GPP2 system refers to the system formulated by wireless standard organization other than the 3GPP2 standard organization, such as Global System For Mobile Communications (GSM) system, GPRS system, WCDMA system and the like formulated by 3GPP organization, WiMax system formulated by IEEE and WMF, Wireless Local Area Network (WLAN) system formulated by IEEE, etc.
At present, in order to realize the intercommunication between the LTE system and the HRPD system, a system architecture shown in FIG. 1 is uniformly employed after a discussion between the 3GPP and the 3GPP2. The two systems are mainly communicated through an S101 interface. Correspondingly, the HRPD needs to be enhanced properly. For example, in order to access an Evolved Packet Core (EPC) in the LTE system through the HRPD system, the original Packet Data Serving Node (PDSN) in the HRPD system is enhanced to be an HRPD Serving Gateway (HSGW) through adding the function of a Mobile Access Gateway (MAG).
Additionally, to realize optimal switching when performing switching from the LTE system to the HRPD system, before the actual switching, dual-mode User Equipment (UE) can perform pre-registration to the HRPD system through Evolved Universal Terrestrial Radio Access (E-UTRAN) system of the LTE. At this time, the message from the HRPD system is required to be capable of being transmitted transparently in a tunnel transmission mode in the E-UTRAN system. Based on hierarchical design features of HRPD air interface protocol, an HRPD message is transmitted in a normal hierarchical structure first; before further transmitted to an HRPD air radio interface for transmission, the HRPD message is required to be forwarded to the air radio interface of the E-UTRAN system for transmission. To avoid modifying physical layer of the HRPD air interface protocol, the 3GPPS adds the function of realizing the HRPD message forwarding to a connection layer of the HRPD air interface protocol, which is taken as a new sub-protocol of the connection layer, i.e., Signalling Adaptation Protocol (SAP). Some high-level sub-protocols of the HRPD air interface protocol are modified correspondingly to adapt to such a change, wherein the enhanced HRPD system is referred to as evolved HRPD (eHRPD) and the enhanced HRPD access network is referred to as evolved Access Network (eAN). On the contrary, the HRPD message, transmitted in a tunnel transmission mode through the LTE air radio interface, is obtained through the SAP, and forwarded to an HRPD processor or re-encapsulated into a message needed to be further forwarded on other interfaces (e.g., S101 interface).
FIG. 2 shows the influenced circumstance of the HRPD air interface protocol after SAP is added to the connection layer. An Inter-Radio Access Technology (Inter-RAT) prefix mark is added before an influenced sub-protocol. Four sub-protocols need corresponding modifications in total, including: initialization state protocol, idle state protocol, route update protocol and overhead message protocol. The uninfluenced sub-protocol in each layer is not shown in FIG. 2.
On the other hand, when an optimized switching is performed from the HRPD system to the LTE system, before dual-mode UE initiates switching, pre-registration to the LTE system is also needed through the HRPD system. At this time, the E-UTRAN message of the LTE system is also required to be capable of being transmitted in a transparent tunnel transmission mode in the HRPD system. As the air interface protocol of the LTE is designed separately according to an Access Stratum (AS) and a Non-Access Stratum (NAS), the E-UTRAN message of the LTE system which needs to be transmitted in tunnel transmission mode is mainly NAS signalling message. At present no effective method about how to identify, encapsulate and transmit transparently these non-3GPP2 messages in a tunnel transmission mode in the HRPD system, such as NAS Signalling message of LTE or corresponding message of WiMax and the like, has been presented.